Polyurethane foams have found extensive use in a multitude of industrial and consumer applications. This popularity is due to polyurethane's wide ranging mechanical properties and the excellent cushioning performance of the foamed product and its ability for the foam to be relatively easily manufactured. Furniture and mattresses, for example, rely on the durability and cushioning performance of polyurethane foams to provide comfort and support over years of use. Automobiles also, contain numerous polyurethane foam components, such as seats, trim and other interior parts. Polyurethane foams have traditionally been categorized as being flexible, semi-rigid or rigid foams. Flexible foams are generally softer, less dense, more pliable and more subject to structural rebound subsequent loading than are rigid foams.
The production of polyurethane foams is well known to those skilled in the art. Polyurethanes are formed from the reaction of NCO groups with hydroxyl groups. The most common method for the production of polyurethanes is reaction of a polyol and an isocyanate which forms the backbone urethane group. Cross linking agents, blowing agents, catalysts and other additives may also be included in the polyurethane formulation as needed.
Polyols used in the production of polyurethanes have typically been petrochemical in origin, being generally derived from propylene oxide, ethylene oxide and various starters such as ethylene glycol, propylene glycol, glycerin, sucrose and sorbitol. Polyester polyols and polyether polyols are the most common polyols used in polyurethane production. For semi-rigid foams, polyester or polyether polyols with molecular weights of from about 300 to 2,000 are generally used. For flexible foams, longer chain polyols with molecular weights of from about 1,000 to 10,000 are typically used. Polyester and polyether polyols can be selected to allow the engineering of a particular polyurethane elastomer or foam having desired final toughness, durability, density, flexibility, compression set ratios and modulus and hardness qualities. Generally, higher molecular weight polyols and lower functionality polyols tend to produce more flexible foams than do lower molecular weight polyols and higher functionality polyols.
Petroleum-derived components such as polyester and polyether polyols pose several disadvantages. Use of such polyester or polyether polyols contributes to the depletion of oil, which is a non-renewable resource. Also, the production of a polyol requires the investment of a great deal of energy because the oil to make the polyol must be drilled, extracted and transported to a refinery where it is refined and processed to yield the finished polyol. As the consuming public becomes increasingly aware of the environmental impact of this production chain, consumer demand for “greener” products will continue to grow. To help reduce the depletion of oil while satisfying this increasing consumer demand, it would be advantageous to partially or wholly replace petroleum-derived polyester or polyether polyols used in the production of polyurethane elastomers and foams with more versatile, renewable and more environmentally responsible components.
One approach taken to address these concerns is the replacement of at least some percentage of the petroleum-based polyols with polyols derived from renewable resources.
Unfortunately, the use of the petroleum-based products is a highly developed industry and years of optimization have created products tailored to meet strict industry requirements. Thus, the attempted substitution of products based on renewable resources has been constrained by several factors including the difficulty of developing “drop in” type products which can be added without significantly affecting the processing characteristics and without substantial loss of product quality. For example, although castor oil-based polyurethanes have been known for decades, their use has generally been limited to a few applications such as hydrophobic coatings and certain sealants where the typical polyurethane properties are not required. There is a continuing need to develop polyethers based on these natural products which can meet industry requirements for foam quality and processability.
The patent and technical literature includes many disclosures in which the use of either castor oil or castor polyols is discussed. (See J. H. Saunders and K. C. Frisch, Polyurethanes Chemistry and Technology II. Technology Part II (High Polymers Vol. XVI), Interscience Publishers, 1964, pages 32-37 and M. Ionescu, Chemistry and Technology of Polyols for Polyurethanes, Rapra Technology Limited, 2005, Chapter 17, pages 435-470. See also published U.S. Patent Application 2007/0238798 and WO 2004/020497). However, production of foam articles that meet the foam processing and property requirements of petroleum based polyols using only a castor oil-based polyol has not yet been achieved.
One approach which has been taken to utilize vegetable oil-based polyols in an effort to reduce the amount of petroleum-based polyols used to produce polyurethanes is use of a polyol component that includes both a petroleum-based polyol and a polyol derived from a renewable resource. See, e.g., U.S. Pat. No. 7,700,661B2, published U.S. Patent Application 2010/0197878A1 and published U.S. Patent Application 2011/0054060A1.
This approach, however, requires more equipment for storage of the individual polyols, blending of the polyols in the required ratio, and storage of the blend prior to use. This approach also requires additional processing steps in the preparation of a suitable polyol blend.
It would therefore be advantageous to develop a polyol derived from a renewable resource that could be used to produce a useful polyurethane foam which could be used without the need to physically blend that polyol derived from a renewable resource with a petroleum-derived polyol.